Revert r316582 [Local] Fix a bug in the domtree update logic for MergeBasicBlockIntoOnlyPred.

Summary: This reverts commit r316582. It looks like this commit broke tests on one buildbot:
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/5719

. . .
Failing Tests (1):
    LLVM :: Transforms/CalledValuePropagation/simple-arguments.ll

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Subscribers:

llvm-svn: 316612

1 files changed, 3 insertions, 7 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 8c643c9..fd33677 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -649,13 +649,9 @@ void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) {
     DestBB->moveAfter(PredBB);
 
   if (DT) {
-    // For some irreducible CFG we end up having forward-unreachable blocks
-    // so check if getNode returns a valid node before updating the domtree.
-    if (DomTreeNode *DTN = DT->getNode(PredBB)) {
-      BasicBlock *PredBBIDom = DTN->getIDom()->getBlock();
-      DT->changeImmediateDominator(DestBB, PredBBIDom);
-      DT->eraseNode(PredBB);
-    }
+    BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
+    DT->changeImmediateDominator(DestBB, PredBBIDom);
+    DT->eraseNode(PredBB);
   }
   // Nuke BB.
   PredBB->eraseFromParent();